Cassette change advice needed

jakeswim145

Hi all, I have recently bought a new bike with Shimano tiagra 4700 groupset on it with a rear 11-25t cassette and short stay derailleur. Ive been struggling on some hills with the gearing and want to try and change to a larger ratio cassette either 28 or 30t. Anyone have any advice on this, will I need to get a new rear derailleur or will I be fine just adding on a new larger cassette?
Thanks all in advanced!!

MiddleRinger

Swapping to a 28T cassette should work with your current rear mech, 30T may be pushing your luck. You'll likely need to fit a longer chain at the same time to compensate.

jakeswim145

Brilliant thanks for that! I thought 30 might be a push, I'll try 28 and see how I get on with it!

svetty

A 30 will likely be fine - might need B screw adjustment but I'd be very surprised if it's a problem. I can use a 30T on an older DA 7900 rear mech without issue...